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Sem 4, case 1 (oesophageal cancer) > intro to epithelial solute and water transport (mini learning) > Flashcards

intro to epithelial solute and water transport (mini learning) Flashcards

1
Q

Which fluids make up the extra cellular fluid ?

A
  • interstitial fluid
  • plasma
  • transcellular fluid (CSF, synovial fluid etc)
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2
Q

Is the GI tract considered internal or external space ?

A

external space

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3
Q

Which membrane of the epithelium faces into the external space ?

A

apical membrane

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4
Q

Which membrane of the epithelium faces into the interstitial space ?

A

basement membrane

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5
Q

What type of membrane junction separate neighbouring cells ?

A

Tight junctions

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6
Q

What type of membrane junction allows for communication between cells ?

A

Gap junctions

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7
Q

What types of membrane junction provide structure to the epithelium ?

A
  • Adhering junction
  • Desmosomes
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8
Q

Are ‘tight junctions’ permeable or impermeable to most ions ?

A

impermeable

leaky to some small ions and water

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9
Q

Are the heads of phospholipids hydrophilic or hydrophobic ?

A

hydrophilic heads

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10
Q

Are the tails of phospholipids hydrophilic or hydrophobic ?

A

hydrophobic tails

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11
Q

What is the function of cholesterol in the phospholipid bilayer?

A
  • provide structural integrity
  • provide precursors for fat soluble vitamins and steroid hormones
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12
Q

Give examples of integral transmembrane proteins …

A
  • membrane transporters (channel proteins etc)
  • G proteins
  • cell surface receptors
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13
Q

What is the phospholipid bilayer impermeable to ?

A
  • Polar molecules
  • Ions
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14
Q

Describe the movement of ions through the sodium-potassium pump …

A

3Na out
2K in
using energy generated in ATP hydrolysis

keeps relative negative charge inside cell = membrane potential

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15
Q

What is the purpose of ion pumps ?

A

creating and maintaining electrochemical gradients

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16
Q

What does the K+ gradient (from the Na-K pump) generate ?

A

membrane potential

= keeping inside of cell less negative, so more positive ions want to diffuse into the cell

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17
Q

What does the Na+ gradient (in the Na-K pump system) drive ?

A

secondary active transport

= drives other passive transporters due to them leaving the cell and creating a more negative gradient inside the cell

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18
Q

What drives passive transport across membranes (ion channels etc) ?

A

the electrochemical gradient

= conc. gradient and membrane potential

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19
Q

Do carrier proteins use active or passive transport ?

A

passive

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20
Q

What determines transport through carrier proteins ?

A

the conc. gradient

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21
Q

What are the 2 subtypes of carrier protein?

A
  • co-transporters
  • exchangers
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22
Q

What does a co-transporter do ?

A

Transports multiple ions into the cell together = symporter

e.g co-transport of glucose

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23
Q

What does an exchanger do?

A

Transports multiple ions in/out of cell but in different directions = antiporter

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24
Q

What kind of active transport do co-transporters and exchangers use ?

A

Secondary active transport

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25
Q

What is meant by secondary active transport ?

A

transporting an ion in the direction of its electrochemical gradient causes another ion to travel against its electrochemical gradient

= active transport using a conc gradient already established by an ion pump

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26
Q

What are the concentrations of Na and K like in intracellular fluid ?

A

Low Na+
High K+

established by the Na-K pump

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27
Q

What are the concentrations of Na and K like in extracellular fluid ?

A

High Na+
Low K+

established by the Na-K pump

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28
Q

What types of diffusion are classed as passive transport ?

A
  • simple diffusion
  • facilitated diffusion
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29
Q

Do molecules move along or against their concentration gradient in passive transport ?

A

along their conc. gradient

high conc to low conc

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30
Q

Do molecules move along or against their concentration gradient in active transport ?

A

against their conc. gradient

low conc to high conc

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31
Q

What channels does water travel through?

A

Aquaporins

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32
Q

Define osmosis …

A

Movement of water from an area of low solute concentration to high solute concentration through a semipermeable membrane

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33
Q

What is osmolarity ?

A

measure of osmotic pressure

34
Q

What are the 3 categories of osmolarity ?

A

Hypertonic = a more solute concentrated solution = water would leave cells placed in a hypertonic solution
Isotonic = solute concentration is in equilibrium with surroundings
Hypotonic = a less solute concentrated solution = water would enter cells placed in a hypotonic solution

35
Q

What % of Saliva secretion comes from the parotid gland when stimulated ?

A

50%

36
Q

Which salivary gland secretes the majority of saliva ?

A

Parotid gland

37
Q

What % of saliva is secreted from the submandibular glands when stimulated ?

A

35%

38
Q

Which salivary gland secretes the least amount of saliva ?

A

sublingual

39
Q

Rank the salivary glands in order of the amount of saliva they secrete (1 = most)…

A
  1. Parotid (60% of saliva from here)
  2. Submandibular (35% of saliva from here)
  3. Sublingual (7-8% of saliva from here)
  4. other minor glands (7-8%)
40
Q

What are serous secretions made up of ?

A

watery
iron-rich

41
Q

What are the 2 components that make up a salivary gland?

A
  • secretory acini
  • ducts
42
Q

What are the 2 types of secretory acini ?

A
  • serous acini
  • mucous acini
43
Q

Which kind of secretory acini do serous secretions come from ?

A

serous acini

44
Q

Which kind of secretory acini do mucous secretions come from ?

A
  • mucous acini
  • serous acini
45
Q

What are the 2 types of saliva secretions ?

A
  • serous secretions (watery)
  • mucous secretions
46
Q

Which is the largest saliva gland?

A

parotid gland

47
Q

What type of saliva does the parotid gland mainly secrete?

A

serous secretions/saliva

watery, iron-rich

48
Q

Which type of secretory acini are found in the parotid gland ?

A

serous acinar cells (acini)

49
Q

Which type of acini are found in the submandibular gland ?

A
  • serous acinar cells (acini)
  • mucous acinar cells (acini)
50
Q

What type of saliva does the submandibular gland secrete?

A

both:
- serous secretions
- mucous secretions

51
Q

What type of saliva does the sublingual gland mainly secrete?

A

mucous secretions

52
Q

Which type of acini are found in the sublingual gland ?

A

mucous acinar cells (acini)

53
Q

What type of saliva does each gland mainly secrete?

A

Parotid = serous
submandibular = both serous + mucous
sublingual = mucous

54
Q

In histology, how can you tell serous acinar cells from mucous acinar cells ?

A

mucous acini = dont stain well/darkly due to being full of mucous

serous acini = stain well/purple

55
Q

Roughly how much saliva is secreted each day ?

A

1 Litre

56
Q

Which inorganic ions are in saliva (in order of highest-lowest conc) ?

A
  1. Na+
  2. HCO3- (bicarbonate)
  3. Cl-
  4. K+
57
Q

How are inorganic ions and water transported out the acinar cells in a salivary glands ?

A
  • ions leave the acinar cells via active transport into the salivary duct
  • water follows via osmosis
58
Q

What are the 2 stages of saliva secretion ?

A
  1. secretion = Na, Cl, bicarbonate + water leave the acinar cells into the duct
  2. reabsorption = NaCl reabsorbed into the duct, saliva leaves hypotonic
59
Q

Is saliva hypertonic, isotonic, or hypotonic ?

A

Hypotonic

= ion conc of saliva is lower than plasma

60
Q

Which transport proteins are preset in the basolateral membranes of acinar cells ?

A
  • Na-K pump (3Na out, 2K in)
  • Na, Cl, K co-transporter (all 3 in)
  • K channel (K out into blood)
  • aquaporins (H2O in)
61
Q

What kind of junction is found between acinar cells in salivary glands ?

A

Tight junction

62
Q

Which transport proteins are preset in the apical membranes of acinar cells ?

A
  • Cl channel (Cl out into duct)
  • aquaporins (H2O out into duct)
63
Q

Which ion moves into the duct through the tight junctions between acinar cells in a salivary gland ?

A

Na+ following the Cl- that makes the duct lumen negative, drawing sodium out

64
Q

Where does modification of primary saliva occur?

A

Salivary duct cells

65
Q

Which ion transporters are found in the basolateral membrane of the salivary duct cells ?

A
  • Na-K pump (3Na out, 2K in)
  • Cl- channel (Cl out into blood)
  • Na - H exchanger (Na in, H out)
66
Q

Which ion transporters are found in the apical membrane of the salivary duct cells ?

A
  • Na+ channel (Na into cell)
  • Cl- channel (Cl into cell)
  • Cl-HCO3 exchanger (Cl in, HCO3 out)
67
Q

What enzyme catalyses the formation of bicarbonate within salivary duct cells ?

A

Carbonic anhydrase

68
Q

How do salivary duct cells differ to acinar cells with regards to water ?

A

Acinar cells = permeable to water via aquaporins

Duct cells = impermeable to water

this causes the saliva to be hypotonic, as water isn’t reabsorbed

69
Q

Is primary saliva hypertonic, isotonic or hypotonic ?

A

isotonic and becomes hypotonic as it travels through the duct

70
Q

Is stimulation of saliva secretion primarily sympathetic or parasympathetic?

A

Parasympathetic stimulation (Ach)

some sympathetic input via NA

71
Q

What is the process of parasympathetic stimulation for saliva secretion ? (detailed version)

A
  1. ACh binds to M1 and M3 receptors
  2. activates signalling cascade that
  3. results in activated G-protein, and
  4. activates phospholipase C enzyme
  5. this increases inositol triphsophate
  6. this triggers Ca2+ release from endoplasmic reticulum
  7. Ca2+ activates ion channels to enable secretion
72
Q

Which parasympathetic neurotransmitter is involved in stimulating saliva secretion ?

A

Acetylcholine

73
Q

What is the action of Ach in the parasympathetic pathway that ultimately triggers salivation?

A

Ach triggers Ca2+ release from endoplasmic reticulum that stimulates K+ and Cl- ion channels

74
Q

Which ion channels does Ca2+ activate in the stimulation pathway of salivation ?

A
  • K+ channels in basolateral membrane of acinar cells
  • Cl- channels in apical membrane of acinar cells
75
Q

Which sympathetic neurotransmitter is involved in stimulating saliva secretion ?

A

Noradrenaline

76
Q

How does the sympathetic pathway affect saliva secretion ?

A

Noradrenaline increases cAMP levels which promotes protein secretion

77
Q

What is the parasympathetic pathway in stimulating saliva secretion ? (simple version)

A
  • ACh binds to muscarinic receptors on acinar cells
  • raises intracellular Ca2+ levels
  • opens ion channels (K+ and Cl-)

= ion + water secretion into salivary duct

78
Q

What is the sympathetic pathway in stimulating saliva secretion ? (simple version)

A
  • Noradrenaline binds to beta-adrenoceptors
  • increases intracellular cAMP
  • promotes protein secretion (mucins, enzymes etc)

= enzyme secretion into the saliva

79
Q

Is saliva acidic or alkaline ? why ?

A

Alkaline

because bicarbonate raises pH

80
Q

Which step of saliva production/secretion results in hypotonic saliva ?

A

Modification of saliva in the salivary ducts

Sem 4, case 1 (oesophageal cancer) (6 decks)

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